<template>
  <div>
    <van-pull-refresh v-model="refreshing" @refresh="onRefresh">
      <van-list
      v-model="loading"
      :finished="finished"
      finished-text="没有更多了"
      @load="onLoad"
    >
      <van-cell v-for="item in list" :key="item" :title="item" />
      </van-list>
    </van-pull-refresh>
    <van-button icon="arrow-up" type="primary" class="backTop" @click="backTop" v-show="flag_scroll">
    </van-button>
  </div>
</template>
<script>
export default {
  data() {
    return {
      list: [],
      loading: false,
      finished: false,
      refreshing: false,
      flag_scroll:false
    };
  },
  mounted() {
    window.addEventListener('scroll', this.handleScroll, true)
  },
  methods: {
    onLoad() {
      setTimeout(() => {
        if (this.refreshing) {
          this.list = []
          this.refreshing = false
        }
        for (let i = 0; i < 10; i++) {
          this.list.push(this.list.length + 1)
        }
        this.loading = false
        if (this.list.length >= 40) {
          this.finished = true;
        }
      }, 1000)
    },
    onRefresh() {
      // 清空列表数据
      this.finished = false;
      // 重新加载数据
      // 将 loading 设置为 true，表示处于加载状态
      this.loading = true;
      this.onLoad();
    },
    backTop(){
      document.body.scrollTop = document.documentElement.scrollTop = 0;
    },
    //methods中定义事件
    handleScroll(env){
      let scrollTop = document.body.scrollTop = document.documentElement.scrollTop
      if(scrollTop > 200){
        this.flag_scroll = true
      }else {
        this.flag_scroll = false
      }
    },
  },
}
</script>
<style lang="less" scoped>
  .backTop {
    position: fixed;
    right: 0.5rem;
    bottom: 3.5rem;
    z-index: 99;
    background-color: rgba(0, 0, 0, 0.25);
    border: 0;
  }
  .van-pull-refresh {
    padding-bottom: 1.5rem;
  }
</style>